Process for recovering metals from solutions



described a similar UNITED STATES PATENT OFFICE raooass For.

aaoovnnma int-raps r'aorr soLu'rrous w Albert a. Doran, Los Angelea,cam, m, to

Dorex, Nevada Ina, -Reno, Nev., a corporation of Serial No. 247,83!

' No Application December 21, me,

10 Claims. (Ol- 75-198) This invention relates to the recovery of metalsfrom their. solutions and more particularly to the recovery of metals inthe form of their insoluble manganites.

It is an object ofthe present invention to provide a process'forrecovering a metal from a so-' lution containing a soluble metal saltcomprising treating or contacting saidsolution with an tigSOlllblEmetallic manganite whereby a metaesis 'which it is desired to recover.the metallic ion originally associated with the manganite being releasedto the solution.

It isiurthermore an object, of the present in-- vention to provide sucha process in which the reacting manganite is associated with a' metalhigher in the electromotiv'e series which it is desired to recover fromsolution.

It is furthermore an object of the present invention to replace heavymetals from :their solutions by the action of an'insoluble alkali'oralkaline earth manganite and to recoversaid heavy metals in the form ofinsoluble manganite salts'.

provide a process for the recovery of metals from their manganite salts,and more particularly from such manganite salts as are produced inaccordance with this invention.

By the term mangani I have here particular reference to salts ofmanganous acid mm,

of which the anhydride MnzOa is well known;

In my copending application Serial No. 203,618, now Patent 2,174,570dated Oct. 3, 1939, I have process for the recovery'of metals in whichuse is made of salts of HzMnOa as the base exchange material, and I havethere used the term "manganite as descriptive of saltsin which theacidic radical contains tctravalent manganese. For purposes of.diilerentiation in the present/specification, I shall use the termpermanganites" for salts containing acidic manganese in the tetravalentfarm andthe term manganite for salts containing acidic manganese in thetrivalent form. The reagent manganite may be advantageously prepared asan alkali manganite, e. g., by alkaline hydrolysis of a manganic salt,or oxidation ofmanganous hydroxide in the presence of an alkali, orreduction of higher valenced compounds of manganese in the presence ofalkali. Usually the compound thus prepared contains substantialquantities of hydrated M11203, a portion of which may be associated withthe desired compound in the form of alkali polymanganites or acidicsalts of alkali ad 'the acid moi. Such or base-exchange is obtainedwhich serves to form an insoluble manganite of the metal than the metalIt is also an object of the present invention to copper.

l'," ganites are also eflective 'in my process. Fre-' quently thepreparation results in the concomitant formation of permanganites,which, as-I have disclosed in'my copending application, are alsoeffective base exchange materials, and I may use such. a mixturecomprising manganites and .permanganites to excellent advantage.

According to their method of production, the manganites may be obtainedin more or less pure form, although it is not necessary for the practiceof my invention that theybe pure. For example,

I may use a mixture in w ch sodiummang n te is associated with e orM11303 or other oxide of manganese. I 1 The manganite salts are ingeneral i y insoluble in water and as usually prepared repre-- sent darkbrown toblack', finely divided solids.

I have discovered that a manganite salt of a given .r'netal has theproperty of replacing from v solution any metal lower in theelectromotive series. For example, I may take a solution of coppernitrate ,in water and add thereto sodium manganite or a sodium manganitebearing mate rial in such proportion that the quantity of sodium isslightly in excess of that chemically equivalentto the copper. Themanganite is suitfind that under these conditions the sodium man-- "ganite is rapidly transformed into copper manganite, the sodiumion'thereby'released being taken up by the solution as nitrate. After asfiflicient period has elapsed to insure the completeness of thereaction, the solution will. be found free from even spectroscopic ofWhen. a very finely divided manganite is used, only a few minutes ofintimate contact are necessary for the-completionof this metathesisorbase 40 exchange.

'Ihein'soluble black powder now hearing: as copper manganite all of thecopper originally present in the solution may be separated from thespent solution by filtration, decantation, or

other suitable method. The copper manganite thus obtained may, if-desired, be used toreplace metals which'lie below copper-in theelectrom0-' tive series. For instance, it brought into contact with asolution of silver nitrate or other soluble silver salt, a silvermanganite will be ob-' tained and copper will be releasedto thesolution-- in equivalent proportion to the silver absorbed. It is notnecessary, however, to proceed through intermediate such as those justindicated,

since silver may be absorbed directly from so- ,at the bottom of thecharge.

lution by the use of an alkali manganite or the manganite r any metallying above silver in the electromotive series.

Having obtained the desired metal in the form of its manganite salt, itmay be further worked up in various ways. For example, it may be treatedwith a solution of a metal still lower in the electromotive series,thereby obtaining an aqueous solution of the desired metal in the formof .a soluble salt. Again, the desired metal manganite may be worked upby various metallurgical methods to obtain the desired metal. In manyinstances the metal may be obtained directly from the manganite salt byheating of the latter. Thus, for example, silver manganite is decomposedat temperatures around 1900 F. to form molten silver metal and variousoxides of manganese, the molten silver collecting as a puddle Gold andother noble metal manganites may be similarly decomposed by heat.

When a solution containing a mixture of vari-' ous metals is treatedwith manganite according to the present process, the absorption ispreferential beginning with the metal which is lowest in theelectromotive series, the remaining metals not being absorbed or beingabsorbed only after the solution is exhausted in the leastelectro-positive metal. 1

An apparent exception to this general rule arises in the case ofhydrogen. Hydrogen ion is displaced from water only with difliculty, ifat all, by a manganite lying above hydrogen in the electromotive series,for example, potassium manganite. 0n the other hand, hydrogen manganite,or manganous acid, does serve as a suitable reagent for the displacementof metals lying below hydrogen in the electromotive series, forexample,copper, silver, or gold, the exchange in this latter: case beingaccomplished readily and without difiiculty, The relative inertness ofdissolved hydrogen ions toward manganites of metals lying above hydrogenin the electromotive series makes itpossibleto' conduct replacementreactions among the compounds of metals higher 5 than hydrogen in theelectromotive series in neutral or even acidic aqueous solutions. Forexample, an aqueous solution of aluminum nitrate may be treated withsodium manganite to obtain an insoluble aluminum manganite and asolution of sodium nitrate, without substantial metathesis between thesodium manganite and water.

In conformity with this behavior, the reagent or base-exchange manganitemay be described as the manganite salt oi any metal or base higher inthe electromotive series than the metal which it is desired to recover,and including the manganite salt of hydrogen (manganous acid). It shouldbernoted, however, that the process is not designed to displace orrecover hydrogen ion from aqueous solutions, and in speaking of therecovery of metals reference is had only to the isting between electrodepotentials and positions in the periodic table.

As above indicated, my invention does not necessitate the use of a puremanganite. The usual method for the formation of a manganite saltresults in the concomitant production of substantial amounts of MnzOa.Such a mixture may be used for the absorption of other metals as abovedescribed. The base exchange efficiency of such a mixture, for example,a mixture as produced by the oxidation of MnOHz in the presence ofpotassium hydroxide, depends on the amount 01' insoluble potassiumpresent in such a mixture, this value corresponding to the proportion oftrue alkali manganite, either in the form of a simple manganite such asKzMnOz or of a complex manganite such as KaMnsOn. When such an impurealkali manganite is used to term other metal manganites according to myprocess, the metal content of the manganite so produced will be found tobe substantiallyequivalent to the original content in insolublepotassium.

In at least some instances I find it preferable to use alkali andalkaline earth manganites for the recovery of less electro-positivemetals, such as the heavy metals, in preference to manganites of othermetals of suitably electropositive character. Furthermore, the alkaliand alkaline earth manganites are the most readily prepared and maycorrespondingly be regarded as primary materials for my process,although it is not intended to imply that it is necessary to start withthese known methods and used as the primary or rev agent manganite.

While it may reasonably be assumed that the active alkaline (or othermetallic) constituent associated with the manganese dioxide in aninsoluble iormis actually present as a true manganite, and properlytermed as such, I do not wish to be bound by any theory as to theprecise molecular structures involved, and where reference is made to amanganite salt, I wish only to imply that the basic oxide and manganesesesquioxide are in an associated or compound form, which form ischaracterized by its insolubility in water and its property of baseexchange as herein described? Various means may be employed forintimately contacting the manganite with the solution to be treated andfor the separation of the manganite and spent solution after treatment.It is frequently advantageous to accomplish these objects in a singlestep, as by percolation of the liquid to'be treated'through a porous bedor diaphragm comprising the, reagent manganite, supported if necessaryon inert granular material.

The details oi. the above examples are illustrative only, the properscope of my invention being delineated in the appended claims.

I claim as my invention:

l. A process for the recovery of a metal from solution, comprising:contacting said solution with 'a manganite salt of a metal moreelectropositive than the desired metal, whereby an insoluble manganitesalt of the desired metal is formed; and separating said insoluble saltfrom the spent solution.

2. A process for the recovery'oi' aheavy metal from its aqueoussolution, comprising: contacting said solution with a finely dividedinsoluble compound oi an oxide of trivalent manganese and an oxideselected from the class consisting of the oxides of the alkali metalsand the alkaline earth metals, whereby said heavy metal replaces thealkali or alkaline earth metal in said compound; and separating saidcompound bearing the heavy metal from the spentsolution.

3. A process for recovery of a metal from solution, comprising:contacting said solution with an insoluble manganite salt of -a metalmore electro-positive than the desired metal, said' man-' ganlte inamount being at least slightly in excess of that chemically equivalentto the metal which it is desired to recover, whereby an insolublemanganite salt of the desired metal and a spent solution substantiallyexhausted in said metal are formed; and separating said insoluble saltfrom the spent solution.

4. A process for recovery of a heavy metal from its aqueous solution,comprising? contacting said solution with aflnely divided insolublecompound of an oxide 01' trivalent manganese and an oxide selected fromthe class consisting of the oxides of the alkali metals and the alkalineearth metals, whereby said heavy metal replaces the alkalior alkalineearth metal in said compound; maintaining said contact until thesolution is substantially exhausted in said heavy metal; and separatingsaid compound bearing the heavy metal from the spent solution.

5. A process for the recovery of a metal from solution, comprising: withan insoluble compound of a base and an oxide of trivalent manganese,said compound having base-exchange properties whereby the base of saidcompound isadapted to exchange with the metal which it is desired toremove from solution:v causing said base-exchange to take place, wherebythe desired metal replaces the base in the manganese compound, saidcompound being taken in amount suiilcient to recover the contacting saidsolution kaline earth metals desired metal substantially completely fromthe solution; separating the insoluble compound thus formed andcontaining the desired metal from the spent solution; and recovering themetal from said insoluble compound.

6. A process as in claim 5, in which the desired metal is gold andinwhich the gold is recovered from the insoluble compound containing saidgold by roasting at elevated temperatures.

7. A process as in claim 5. in which the desired metal is silver andrecovered from the insoluble compound containing said silver by roastingat elevated temperatures.

8. A process for the recovery of a metal from solution. comprising:contacting successively flowing increments of the solution to be treatedwith an insoluble compound of a base and an oxide 01 trivalentmanganese, said compound having base-exchange properties whereby thebase of said compound is adapted-to exchange with the metal'which itisrlesh'ed to remove from solution; causing said base-exchange to takeplace with each increment of solution, whereby the desired metalprogressively replaces the base in the manganese compound; andseparating the spent increments of solution from further contact withsaid compound.

9. A process for recovering a heavy metal from a dilute aqueous solutionthereof, comprising soluble manganite of a metal of the group consistingof alkali and alkaline earth metals to form an insoluble manganite ofthe heavy metal and a solution substantially free 01' said metal;separating the insoluble. manganite from the spent solution; andrecovering the heavy metal from said manganite.

10. A process as in claim 8, in which the base 10 in which the silverisoriginally associated with the manganese oxide is 40 a metal of theclass constituted by alkali and aland in which the recovered metal is aheavy metal. l

' ALBERT B. DOB-AN.

30v contacting the dilute aqueous solution with an in-

